This invention is generally directed to liquid developer compositions, especially colored liquid developers with rapid drying times, and excellent image fixing characteristics. More specifically, the present invention is directed to colored liquid developer compositions comprised of an oil base, a sterically stabilized latex component, and other additives, inclusive of thickeners. Thus, in one important embodiment of the present invention there are provided liquid inks with rapid drying times, less than 40 seconds for example, and excellent image fixing characteristics, which inks are comprised of a Magiesol-isopar oil base or oil base mixture, a dyed latex of poly(vinyl pyrrolidone-co-ethylacrylate) sterically stabilized with a soluble polymer, inclusive of polyisobutylene, or poly(styrene-b-ethylene butylene) block copolymer, and a thickener component. In a further embodiment of the present invention there are provided liquid ink compositions comprised of an oil base component, a sterically stabilized latex component dyed with a cyan, magenta, or yellow dye, or mixtures thereof; and a thickener component. The liquid inks of the present invention can be selected for the development of images in various processes including the liquid development process as described in U.S. Pat. No. 3,084,043, the disclosure of which is totally incorporated herein by reference; xerographic processes, electrographic recording, electrostatic printing, and facsimile systems.
Liquid developer compositions are known, reference for example U.S. Pat. No. 3,806,354, the disclosure of which is totally incorporated herein by reference. This patent illustrates liquid inks comprised of one or more liquid vehicles, colorants, such as pigments, dyes, dispersants, and viscosity control additives. Examples of vehicles disclosed in the aforementioned patent are mineral oils, mineral spirits, and kerosene; while examples of colorants include carbon black, oil red, and oil blue. Dispersants described in this patent include materials such as alkylated polyvinyl pyrrolidone. Additionally, there is described in U.S. Pat. No. 4,476,210 electrostatically charged liquid developers containing an insulating liquid dispersion medium with marking particles therein, which particles are comprised of a thermoplastic resin core substantially insoluble in the dispersion, an amphipathic block or graft copolymeric stabilizer irreversibly chemically, or physically anchored to the thermoplastic resin core, and a colored dye imbibed in the thermoplastic resin core. The history and evolution of liquid developers is provided in the '210 patent, reference columns 1 and 2 thereof. Also of interest are the liquid inks disclosed in U.S. Pat. Nos. 4,004,931 and 4,268,597, see columns 13, 23 and 24, wherein an ink developer with a dye dissolved in an oil vehicle is illustrated. A similar teaching is presented in U.S. Pat. No. 3,772,012, see columns 7 and 8; U.S. Pat. No. 3,985,663, see columns 3, 4, 5 and 9; and U.S. Pat. No. 4,202,913, see columns 7, 15 and 17.
In addition, there is disclosed in U.S. Pat. No. 4,197,211 an ink composition having suspension of colored resin particles, reference columns 5, 6, 7 and 10; and in 4,245,023 there is described a process for the development of electrostatic images on dielectric paper, reference column 7, and note the general statement in column 8 that the developing liquid may be a solution or a suspension. Moreover, the use of vinyl pyrrolidones and ethylacrylates in developers is illustrated in U.S. Pat. Nos. 4,497,866, see the Abstract of the Disclosure; 3,383,209, see column 18; 3,441,426, see column 4; and 3,907,695. References of general background interest include U.S. Pat. Nos. 3,372,027; 3,486,922; 3,954,640; 4,024,292; and 4,062,789. These references, however, do not teach a colored liquid developer composition with an insulating oil base, a stabilized latex component with imbibed molecularly dispersed colored dyes, and a thickener.
Although the above described liquid inks are suitable for their intended purposes, there remains a need for new liquid developers. More specifically, there is a need for colored liquid developers with improved drying times, excellent image fixing characteristics, desirable conductivity values, and which exhibit time independent non-Newtonian rheological properties. Additionally, there is a need for submicron colored liquid developer compositions that permit images of excellent resolution in a number of known imaging processes, including those illustrated in U.S. Pat. No. 3,084,043. Moreover, there is a need for liquid developers wherein the dyes selected are suitably dispersed thus enabling colored images of excellent resolution. Further, there remains a need for colored latex liquid developers wherein there are included therein other additives including thickeners, and wherein these developers have a desirable conductivity of from about 10.sup.9 to about 10.sup.11 (ohm-cm).sup.-1. There also is a need for colored latex liquid inks which are useful with dielectric papers. Moreover, the dye latex ink particles of the present invention are essentially of a neutral polarity and oil based liquids as contrasted, for example, with pigments which often charge when placed in oils. Accordingly, with the conductive liquid inks of the present invention with neutral polarities thereon images of either a positive or negative charge can be developed. In addition, there is a need for liquid developers with a latex of a soft or hard component thereby enabling the thermal mechanical properties to be selected as desired enabling, for example, acceptable fixing characteristics. There is also a need for colored liquid inks wherein the polymer particles can be dyed to any desired color. Also, there is a need for liquid inks that are thermal dynamically stable, that is for example they do not flocculate on standing; and further, there is a need for inks with extended shelf life for periods exceeding six months.